Let me thank all the great guys who responded to my query so fast. Here are the excerpts from the mails that I received. The reason is "minfree" taking some bytes out from the user. And Paul also suggests that fragmentation may add to it further. Thanks to all of you, Ramesh Michael Schulte =========== The standard file system reserves about 10% of the kbytes for efficiency; it is unavailable to anyone except root. Notice that the used+avail != kbytes. VAleriy ======== If you created your filesystem with default options, 10% of the space was reserved for root only access. So, in reality, you have to divide it by (0.9*963869), i.e. 963869kb available total, take 10% for root only writes and you'll get 867462.1, now 185680/867462.1 = 21% see man newfs section for -m option Tom Payerle ========= On Unix filesystems, there is typically some portion of a filesystem which is reserved for root only; i.e. once a filesystem is filled to a certain point, only root can write to it. This is useful for stuff like / and /usr to enable things to work pretty well even when filesystems get "full". I think the mkfs/newfs commands default to about 5% for this root reservation. Some systems (I forget whether Solaris has this) have tunefs type commands that can alter it once the filesystem is up and running, others it must be done at creation time. In your root case, used (185680) + avail (720357) = 906037 or 57832 less than in kbytes field. (which is 6% of the total). Note that 185680/906037 = 20.5% This 5% or so reservation is probably not worth bothering with on a 1-2GB system disk or partitions (/, /usr, /var, etc). It probably is worth messing with when dealing with 10 GB or more data only partitions (e.g. the system can function pretty well if partition was missing), although to be honest even in those cases I usually haven't done anything about it. Tom Payerle Dept of Physics payerle@physics.umd.edu University of Maryland (301) 405-6973 College Park, MD 20742-4111 Fax: (301) 314-9525 ID16314 Explanation of file system usage as reported by df and fsck Paul Richards ============== :df output : Filesystem kbytes used avail capacity ... :/dev/sd2d 1961966 1745945 19825 99% ... :1961966 kbytesFile system size :1745945kbytes usedAmount used :19825 kbytes freeEqual to (size less minfree%) less used :99%Equal to used as % of (size less minfree%) so minfree can affect the answer also fragmentation can have an effect :For example, in a file system that creates predominantly 5k files on an :8k block size there will be many 3k frags free and never used. In the :extreme case this would result in a file system that is effectively :full despite only 5/8 of the filesystem being used. Jay Lessert ======== minfree. Looks like / was built with 6% minfree and /usr with 2% minfree. /: 185680/(0.94 * 963869) = 20.5% /: 2263070/(0.98 * 3099093) = 74.51% You can see current minfree (and lots of other interesting information about a file system with: % sudo fstyp -v /dev/rdsk/c0t0d0s0 Crist J. Clark ======== Read df(1), -k Print the allocation in kbytes. The output consists of one line of information for each specified file sys- tem. This information includes the file system name, the total space allocated in the file system, the amount of space allocated to existing files, the total amount of space available for the creation of new files by unpriviledged users, and the percentage of ^^^^^^^^^^^^^ normally available space that is currently allocated to all files on the file system. This option overrides the -b, -e, -n, and -t options. And newfs(1M), -m free The minimum percentage of free space to maintain in the file system (between 1% and 99%, inclusively). This space is off-limits to normal users. Once the file system is filled to this threshold, only the super-user can continue writing to the file system. This parameter can be subsequently changed using the tunefs(1M) command. The default is ((64 Mbytes/partition size) * 100), rounded down to the nearest integer and limited between 1% and 10%, inclusively. Lars ==== man newfs(1m), -m option. capacity = used / ( used + avail ) used + avail < kbytes. -- Omnibiblious, adj.: Indifferent to type of drink. "Oh, you can get me anything. I'm omnibiblious." Eugene ========= Hi By default a certain amount of space is allocated as "reserved for root use only". This space is also commonly referred to as "slosh space". This can be modified with tunefs (see man page). The calculation takes this into account. Typically this is between 1 and 10 %, depending on the FS size. -----Original Message----- The % available is based on the 90% level of capacity: /: ( 185680 / (.90 * 963869)) = 21% Mark ========== thats because when you do a defualt newfs it save 10% for superuser.. man newfs and look for the -m option: -m free The minimum percentage of free space to maintain in the file system. This space is off-limits to normal users. Once the file system is filled to this threshold, only the super-user can continue writing to the file system. This parameter can be subsequently changed using the tunefs(1M) command. The default is 10%. So with a newfs -m 3 /dev/dsk/c0t0d0s0 will give you 7% more disk space for that partition... Hope this helps... Kevin ===== The capacity percentage reported by "df -k" is the amount of user writable space that is in use. What you're calculating is the total amount of space that is in use. By default, UFS filesystems reserve 10% of the space in the filesystem that can only be written to by root (as an aside, this can and should be changed when large filesystems are created; 10% of a 1 TB filesystem is a lot of wasted space). This is also why you can see filesystems that are more than 100% full. HTH... ================================== Kevin Buterbaugh - Systems Engineer LifeWay - www.lifeway.com Man tunefs Look at the -m Option and it was clearer ;-) -- Michael Schneider MM-ITconsulting Sun Certified Network Administrator Ph: +49(0)700 Ramesh C Pathak Vinciti Networks Pvt. Ltd., #1109, 24th Main Road, JP Nagar 1st Phase, Bangalore - 560 078 Ph: +91-80-6556830 Fax: +91-80-6556820 email: ramesh.pathak@vinciti.com URL: http://www.vinciti.com This information is intended only for the use of the individual to whom it is addressed and may contain information that is privileged, confidential and exempt from disclosure under law. If you are not the intended recipient, you are hereby notified that any use, dissemination, distribution or copying of this communication is strictly prohibited. _______________________________________________ sunmanagers mailing list sunmanagers@sunmanagers.org http://www.sunmanagers.org/mailman/listinfo/sunmanagersReceived on Wed Aug 27 19:33:08 2003
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